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Abstract:

A network node, in particular, for a sensor network, is configured to
receive sensor data from at least one further network node transmitting
the sensor data. The network node has a time stamp device, which is
configured to assign received sensor data values time stamps, which
represent a time of reception of the sensor data values at the network
node with respect to a primary time reference assigned to the network
node.

Claims:

1. A network node, which is for a sensor network, the network node being
configured to receive sensor data from at least one further network node
transmitting the sensor data, comprising: a time stamp device, which is
configured to assign received sensor data values to time stamps, which
represent a time of reception of the sensor data values at the network
node with respect to a primary time reference assigned to the network
node.

2. The network node of claim 1, wherein the receiving network node is
configured to ascertain parameters of a secondary time reference of the
transmitting network node sending the sensor data, at least one of: (i)
as a function of at least one of a frame length and a symbol transmission
rate of the received sensor data, (ii) as a function of characteristic
pulse shapes or pulse patterns, and (iii) as a function of characteristic
patterns of the data stream that contains the sensor data.

3. The network node of claim 2, wherein the network node is configured to
establish a relationship between the primary time reference and the
secondary time reference as a function of the ascertained parameters of
the secondary time reference.

4. The network node of claim 1, wherein the network node is configured to
at least one of sectionally reconstruct and partially reconstruct a
sensor signal originally acquired by the transmitting network node, from
the received sensor data values, using at least one of the time stamps
and a relationship between the primary time reference and the secondary
time reference.

5. The network node of claim 1, wherein the network node is configured to
transmit a trigger signal to at least one further network node, and
wherein in the at least one further network node, the trigger signal
triggers at least one of (i) an acquisition of a sensor signal, and (ii)
the transmission of sensor data to the network node.

6. The network node of claim 1, wherein the network node is configured to
transmit periodically a trigger signal to at least one further network
node, so as to synchronize a secondary time reference of the further
network node with the primary time reference.

7. A network node, which is for a sensor network, comprising: an
acquiring arrangement to acquire at least one sensor signal; and a
transmitting arrangement to transmit sensor data characterizing the
acquired sensor signal to at least one network node receiving the sensor
data; wherein the network node is configured to transmit the sensor data
to the receiving network node as a function of a secondary time
reference, which is assigned to the network node and which is
asynchronous with respect to a primary time reference of the receiving
network node.

8. The network node of claim 7, wherein the network node is configured to
receive a trigger signal and to at least one of (i) acquire the sensor
signal, and (ii) transmit sensor data to the network node as a function
of the trigger signal.

9. The network node of claim 7, wherein the network node is configured to
receive a trigger signal and to synchronize its secondary time reference
with a primary time reference of a network node sending the trigger
signal, as a function of the trigger signal.

10. The network node of claim 7, wherein the network node is configured
to calculate an average value over a plurality of sampling values of the
acquired sensor signal, and to transmit the average value to the
receiving network node.

11. The network node of claim 7, wherein the network node is configured
to perform a data compression over a plurality of sampling values of the
acquired sensor signal, and to transmit compressed sensor data to the
receiving network node.

12. A method for operating a network node, which is for a sensor network,
the network node being configured to receive sensor data from at least
one further network node transmitting the sensor data, the method
comprising: assigning, using the network node, with the aid of a time
stamp device, received sensor data values to time stamps, which represent
a time of reception of the sensor data values at the network node with
respect to a primary time reference assigned to the network node.

13. The method of claim 12, wherein the network node ascertains
parameters of a secondary time reference of the transmitting network node
sending the sensor data, at least one of (i) as a function of at least
one of a frame length and a symbol transmission rate of the received
sensor data, (ii) as a function of characteristic pulse shapes or pulse
patterns, and (iii) as a function of characteristic patterns of the data
stream that contains the sensor data.

14. The method of claim 12, wherein the network node at least one of (i)
establishes a relationship between the primary time reference and the
secondary time reference as a function of the ascertained parameters of
the secondary time reference, and (ii) at least one of sectionally
reconstructs and partially reconstructs a sensor signal originally
acquired by the transmitting network node, from received sensor data
values, using at least one of the time stamps, and the relationship
between the primary time reference and the secondary time reference.

15. The method of claim 12, wherein the network node transmits a trigger
signal to at least one further network node, so as to at least one of (i)
trigger, in the at least one further network node, at least one of an
acquisition of a sensor signal and the transmission of sensor data to the
network node, and (ii) synchronize a secondary time reference of the
further network node with the primary time reference.

Description:

RELATED APPLICATION INFORMATION

[0001] The present application claims priority to and the benefit of
German patent application no. 10 2010 044 208.9, which was filed in
Germany on Nov. 22, 2010, the disclosure of which is incorporated herein
by reference.

FIELD OF THE INVENTION

[0002] The present invention relates to a' network node, in particular,
for a sensor network, the network node being configured to receive sensor
data from at least one further network node transmitting the sensor data.
The present invention further relates to an operational method for such a
network node. In addition, the present invention relates to a network
node, in particular, for a sensor network, the network node being
configured to acquire at least one sensor signal and to transmit sensor
data characterizing the acquired sensor signal to at least one network
node receiving the sensor data. The present invention further relates to
an operational method for such a network node.

BACKGROUND INFORMATION

[0003] A network node of the type mentioned above is discussed in US
2007/0219751A1. The network node is configured to provide an acquired
sensor signal with time stamps and to transmit the sensor signal,
together with the time stamps, to another device. This demands a large
amount of structural expenditure, because the time stamps must be applied
to the sensor signal locally, that is, in a sensor network node. The
provision of a highly precise time reference in the sensor network node
is necessary for this. Furthermore, the sending of the acquired sensor
signal, as well as associated time stamps, has the significant
disadvantage that a payload data bandwidth of the transmission medium is
reduced by sending the time stamps along, which means that fewer sensor
data per unit time may be transmitted to a receiving network node.

SUMMARY OF THE INVENTION

[0004] Accordingly, an object of the exemplary embodiments and/or
exemplary methods of the present invention is to improve a network node
and an operational method for a network node of the type mentioned at the
outset, such that the above-mentioned disadvantages of the related art
are eliminated.

[0005] This object is achieved in a network node of the type mentioned at
the outset, in that the network node has a time-stamp device, which is
configured to assign received sensor data values time stamps that
represent a time of reception of the sensor data values at the network
node with respect to a primary time reference assigned to the network
node.

[0006] In this manner, one may advantageously dispense with a network node
transmitting the sensor data having to perform time stamping itself, as
well as with the sensor data having to be transmitted, together with the
time stamps, to a receiving network node. In an advantageous manner, the
network nodes of the exemplary embodiments and/or exemplary methods of
the present invention that receive the sensor data may themselves
undertake time stamping, which defines the entry time of the received
sensor data with respect to the primary time reference of the receiving
network node, so that subsequent processing of the received sensor data
may be carried out independently of any delay times in the receiving
network nodes.

[0007] A further advantage of the exemplary embodiments and/or exemplary
methods of the present invention is that the complete transmission
bandwidth of a communication interface, which is normally digitally
formed and is between a transmitting network node acquiring the sensor
signals and the receiving network node of the exemplary embodiments
and/or exemplary methods of the present invention, may be used for
transmitting sensor data and does not have to be used for transmitting
time stamps.

[0008] In an advantageous specific embodiment, it is provided that the
network node be configured to ascertain parameters of a secondary time
reference of the network nodes sending the sensor data, as a function of
a frame length and/or a symbol transmission rate of the received sensor
data. Analyses of the applicant have revealed that in the case of a
digital data transmission between the transmitting network node and the
receiving network node of the exemplary embodiments and/or exemplary
methods of the present invention, it is advantageously possible to
ascertain information about the time base or time reference of the
transmitting network node by evaluating an arrival time of the frame of
the digital transmission and/or a frame length and/or a symbol
transmission rate of the digitally transmitted signal. This means that
although the exemplary embodiments and/or exemplary methods of the
present invention may not provide any transmission of time stamp
information from a transmitting sensor network node to the receiving
network node, the receiving network node may advantageously obtain such
information or at least parameters that characterize a secondary time
reference of the transmitting network node, from the received signal.

[0009] In a further advantageous, specific embodiment, it is provided that
the network node be configured to establish a relationship between the
primary time reference and secondary time reference as a function of the
ascertained parameters of the secondary time reference. With knowledge of
such a temporal relationship, the signal acquired at the transmitting
(sensor) network node, or corresponding sampling values, may be clearly
deduced in an advantageous manner from the sensor data presently in the
receiving network node that are provided with a time stamp.

[0010] In a particularly advantageous manner, the network node is
configured to at least sectionally and/or partially reconstruct a sensor
signal originally acquired by the transmitting network node, from the
received sensor data values, using the time stamps and/or the
relationship between the primary time reference and the secondary time
reference. The sectional reconstruction may refer to predefined,
interesting time intervals of the sensor signal, for example. In
addition, a partial reconstruction may also include further signal
processing, such that, e.g., only certain frequency components of the
sensor signal are reconstructed as a function of the received sensor
data.

[0011] In a further advantageous, specific embodiment, the network node is
configured to transmit a trigger signal to at least one further network
node, in particular, to the network node sending the sensor data; in the
at least one further network node, the trigger signal triggering the
acquisition of a sensor signal and/or the transmission of sensor data to
the network node. In this manner, in spite of the essentially
asynchronous operation of the transmitting network node with respect to
the receiving network node, it is possible to control, to a certain
extent, the acquisition of the sensor signal or the transmitting of
sensor data, starting out from the receiving network node.

[0012] In a further advantageous, specific embodiment, it is provided that
the network node be configured to periodically transmit a trigger signal
to at least one further network node, in order to synchronize a secondary
time reference of the further network node with the primary time
reference.

[0013] A network node according to the description herein is specified as
a further way to achieve the object of the exemplary embodiments and/or
exemplary methods of the present invention. The network node of the
exemplary embodiments and/or exemplary methods of the present invention
is configured to acquire at least one sensor signal and to transmit
sensor data characterizing the acquired sensor signal to at least one
network node receiving the sensor data. In addition, the network node of
the exemplary embodiments and/or exemplary methods of the present
invention is characterized in that it is configured to transmit the
sensor data to the receiving network node as a function of a secondary
time reference, which is assigned to the network node and is, in
particular, asynchronous with respect to a primary time reference of the
receiving network node. This allows a design of the transmitting network
node (sensor network node) having a particularly low degree of
complexity, since the time stamping or a permanent synchronization of the
transmitting network node with the network node receiving the sensor data
may be dispensed with.

[0014] In an advantageous further refinement, the network node is
configured to receive a trigger signal and to acquire the sensor signal
and/or transmit sensor data to the network node as a function of the
trigger signal.

[0015] The network node may further receive the trigger signal and, as a
function of the trigger signal, synchronize its own, secondary time
reference with a primary time reference of a network node sending the
trigger signal.

[0016] In a further advantageous, specific embodiment, it is provided that
the network node be configured to calculate an average value over a
plurality of sampling values of the acquired sensor signal, and to
transmit the average value to the receiving network node. This specific
embodiment is then particularly advantageous, if there is a relatively
high sampling rate in the network node evaluating the sensor signal, and
if data frames are to be sent to a receiving network node at only a
relatively low frequency or transmission rate.

[0017] In a further advantageous, specific embodiment, the network node is
further configured to perform data compression over a plurality of
sampling values of the acquired sensor signal, and to transmit compressed
sensor data to the receiving network node.

[0018] A method for operating a network node according to the description
herein is specified as one more further ways to achieve the object of the
exemplary embodiments and/or exemplary methods of the present invention.
According to the exemplary embodiments and/or exemplary methods of the
present invention, the network node assigns time stamps to received
sensor data values, using a time stamp device, the time stamps
representing a time of reception of the sensor data values at the network
node with respect to a primary time reference assigned to the network
node.

[0019] Further advantageous refinements are the subject matter of the
further descriptions herein.

[0020] Additional features, uses and advantages of the exemplary
embodiments and/or exemplary methods of the present invention are derived
from the following description of exemplary embodiments of the present
invention, which are illustrated in the figures of the drawing. In this
context, all of the described or illustrated features form the subject
matter of the present invention, either alone or in any combination,
irrespective of their combination in the patent claims or their
antecedent references, and also irrespective of their wording and
illustration in the description and in the drawings, respectively.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG. 1 shows schematically, a sensor network having a receiving
network node according to a first specific embodiment, and having a
transmitting network node according to a further specific embodiment of
the present invention.

[0022] FIG. 2 shows a further specific embodiment of the sensor network
according to the present invention.

[0023] FIGS. 3a, 3b, 3c, 3d, and 3e show a time characteristic of
different operating variables of the sensor network according to the
present invention.

[0024] FIG. 4 show a simplified flow chart of a specific embodiment of the
operational method according to the present invention.

[0025] FIG. 5 show a simplified flow chart of a further specific
embodiment of the operational method according to the present invention.

[0027] Although the specific communication of network nodes 100, 200 is
not necessarily limited to one communication direction (send/receive),
for the following description, network node 100 is also referred to,
inter alia, as a receiving network node, since it receives sensor data sd
from further network node 200. Accordingly, the network node 200
transmitting sensor data sd is also referred to below, inter alia, as a
transmitting network node.

[0028] Network nodes 100, 200 form a sensor network, as is provided, for
example, in the area of motor vehicles for acquiring sensor data and for
transmitting acquired sensor data sd to a receiving network node 100.
Accordingly, in addition to transmitting network node 200, further
transmitting network nodes 200a, 200b may also be provided in the sensor
network, the functionality of the further transmitting network nodes
essentially corresponding to that of transmitting network node 200 and
not being described in further detail above.

[0029] Transmitting network node 200 is used for acquiring at least one
sensor signal y(t), which may be, for example, a time-continuous or
value-continuous signal, such as a voltage signal of a pressure sensor or
the like. Transmitting network node 200 has a secondary time reference
202, which is integrated into transmitting network node 200, as is
apparent from FIG. 1, which means that transmitting network node 200 may
use it for controlling its operation. In particular, time reference 202
of transmitting network node 200 is independent of a primary time
reference 102 of receiving network node 100 and is normally asynchronous
with respect to it.

[0030] Transmitting network node 200 acquires sensor signal y(t), for
example, using an analog-to-digital (AD) converter, which is not shown in
FIG. 1 and samples sensor signal y(t) in a manner known per se. The A/D
converter may also be integrated into signal processing unit 204 of
transmitting network node 200, for example. Digital sensor data, which
are obtained from sensor signal y(t) by signal processing unit 204, are
transmitted to digital data transmission unit 206 of transmitting network
node 200, the digital data transmission unit transmitting these to
receiving network node 100 in the form of sensor data sd. The digital
transmission takes place as a function of secondary time reference 202,
in the same manner as the processing by signal processing unit 204.

[0032] Next to its primary time reference 102, receiving network node 100
has a counter 104 that supplies a counter value under the control of
primary time reference 102. The counter value is supplied to a time stamp
device 106, which, according to a particular variant of the exemplary
embodiments and/or exemplary methods of the present invention, generates
a time stamp cnt(i) from the counter value and supplies time stamp cnt(i)
to data processing device 110. Received sensor data values sd(i) and
corresponding time stamps cnt(i) are combined with each other in data
processing device 110, which may contain a memory, as well; each received
sensor data value sd(i) being assigned a corresponding time stamp value
cnt(i). In this connection, a time stamp value cnt(i) represents the time
of reception, at network node 100, of a particular sensor data value
sd(i) assigned to the time stamp value, with respect to the primary time
reference 102 assigned to network node 100.

[0033] This means that the time of reception of a sensor data value sd(i)
in receiving network node 100 may be deduced from time stamp cnt(i) of
sensor data value sd(i).

[0034] Therefore, a subsequent evaluation of received sensor data sd or of
individual sensor data values sd(i) by evaluation unit 112 may be
temporally triggered, thus, in particular, independently of a
transmission rate at which sensor data sd are received at receiving
network node 100.

[0035] In an advantageous specific embodiment, receiving network node 100
is configured to ascertain parameters of secondary time reference 202 of
the transmitting network node 200 sending sensor data sd, as a function
of a frame length and/or a symbol transmission rate of received sensor
data sd and/or as a function of characteristic pulse shapes or pulse
patterns and/or as a function of characteristic patterns of the data
stream that contains sensor data sd. In a particular manner, the nominal
periods of time of these characteristics of transmitted data sd and
signals of transmitting network node 200 are known to receiving network
node 100, which means that it may relate the data and measured values
y(t) determined by transmitting time reference 202 to its primary time
reference 102. In this case, receiving network node 100 may therefore
advantageously deduce the characteristics or a clock frequency of
secondary time reference 202 of transmitting network node 100, which
means that, inter alia, synchronization or at least the generation of a
time relationship between primary time reference 102 of receiving network
node 100 and secondary time reference 202 of transmitting network node
200 is rendered possible.

[0036] The determination of the parameters of secondary time reference 202
is carried out by a timing recovery unit 108 of receiving network node
100, the timing recovery unit having a data connection to digital
transmission interface 108.

[0037] In a further advantageous, specific embodiment, receiving network
node 100 is configured to establish a relationship between primary time
reference 102 and secondary time reference 202 as a function of the
determined parameters of secondary time reference 202. This relationship
between the two time references 102, 202 may be advantageously stored in
memory 110 in a manner analogous to time stamp cnt(i), so that it is
available for a later evaluation by block 112.

[0038] In a further advantageous, specific embodiment, it is provided that
receiving network node 100 be configured to at least sectionally and/or
partially reconstruct a sensor signal y(t) originally acquired by
transmitting network node 200, from received sensor data values sd(i),
using time stamps cnt(i) and/or the relationship between primary time
reference 102 and secondary time reference 202.

[0039] For example, using such an evaluation, receiving network node 100
may reconstruct all of the sampling values at time t0, t1, t2, t3, t4 of
sensor signal y(t), as they were also obtained by transmitting network
node 200.

[0040] Alternatively, receiving network node 100 may also only reconstruct
selected sampling values, e.g., every second sampling value at time t0,
t2, t4. It is also possible for receiving network node 100 to interpolate
sensor signal y(t), e.g., using splines.

[0041] Using resampling methods known per se, a series of sensor data
values may also be converted from a first sampling frequency, as is
defined by transmitting network node 200, to a second sampling frequency,
as is provided, e.g., to a further digital signal processing in the scope
of evaluation unit 112 or a further device (not shown).

[0042] FIG. 2 shows a sensor network according to a further specific
embodiment of the present invention. A network node 100a comparable to
network node 100 of FIG. 1 additionally has a trigger device 114, with
the aid of which receiving network node 100a may transmit a trigger
signal ts to transmitting network node 200. Transmitting network node 200
has a trigger receiving device 208 for receiving trigger signal ts, the
trigger receiving device being able to act, for example, upon internal
time reference 202 or also upon signal processing unit 204.

[0044] This means that by emitting trigger signal ts, receiving network
node 100a may signal to transmitting network node 200, that sensor data
values should be acquired or transmitted.

[0045] Trigger signal ts may be sent, and in particular, periodically, by
receiving network node 100a to transmitting network node 200 as a
function of primary time reference 102. In this case, secondary time
reference 202 of transmitting network node 200 may also advantageously
synchronize itself with primary time reference 102, since information
establishing the temporal relationship between time references 102, 202
is formed periodically by trigger signal ts.

[0046] Alternatively or additionally, receiving network node 100a may also
emit trigger signal ts as a function of an external trigger signal ts',
which the receiving network node 100a obtains from an external source
such as a control unit of a motor vehicle or the like.

[0047] In the time characteristic of sensor signal y(t) of FIG. 2, a
triggering time t0 corresponding to trigger ts is symbolized by a block
arrow T at time t0.

[0048] In a further advantageous, specific embodiment of network node 200,
it is provided that network node 200 be configured to calculate an
average value over a plurality of sampling values of acquired sensor
signal y(t), and to transmit the average value to receiving network node
100. This variant of the exemplary embodiments and/or exemplary methods
of the present invention may be used in a particularly advantageous
manner, when a sampling rate of sensor signal y(t) by transmitting
network node 200 is relatively large in comparison with a transmission
rate of data frames, as are transmitted by transmitting network node 200
to receiving network node 100a in order to route sensor data sd to
receiving network node 100a.

[0049] In a further advantageous, specific embodiment of network node 200,
it is provided that network node 200 be configured to perform data
compression over a plurality of sampling values of acquired sensor signal
y(t), and to transmit compressed sensor data to receiving network node
100, 100a.

[0050] In an advantageous manner, the further signal processing steps
described above (averaging, data compression) may be executed, in turn,
by a signal processing unit 204 of transmitting network node 200.

[0051] FIGS. 3a) to 3e) each show a time characteristic of different
operating variables of the sensor network according to FIG. 2

[0052] FIG. 3a) shows a characteristic curve of trigger signal ts, as is
output by receiving network node 100a to transmitting network node 200.
The time characteristic of trigger signal ts is plotted over a time axis
t100, which corresponds to primary time reference 102 of receiving
network node 100a.

[0053] FIG. 3b) shows a time characteristic of sampling values, as are
obtained by transmitting network node 200 by sampling sensor signal y(t)
in reaction to the reception of trigger signal ts. The sampling values
according to FIG. 3b) are plotted over a time axis t200, which
corresponds to secondary time reference 202 of transmitting network node
200.

[0054] It is apparent from FIG. 3b) that in the exemplary embodiment
described above by way of example, a total of three sampling values are
obtained by transmitting network node 200 in reaction to the reception of
each trigger signal ts. The transmission of corresponding sensor data sd
takes place in a close temporal relationship with the determination of
the corresponding sampling values from FIG. 3b; see also FIG. 3c) for
comparison, which represents the time characteristic of sensor data sd,
as are transmitted to receiving network node 100a.

[0055] FIG. 3d) shows combinations obtained according to the exemplary
embodiments and/or exemplary methods of the present invention, the
combinations being of, in each instance, a sensor data value sd(i), as is
obtained at the output of digital communication interface 108 of
receiving network node 100a, and a corresponding time stamp cnt(i), as is
assigned to the corresponding sensor data value sd(i) by time stamp unit
106 of the exemplary embodiments and/or exemplary methods of the present
invention.

[0056] Finally, FIG. 3e) shows the time characteristic of a further
processing of the sensor data values sd(i) provided with time stamp
cnt(i), as may be performed, for example, by evaluation unit 112 of
receiving network node 100a.

[0057] From FIG. 3e), it is apparent that the combinations of sensor data
values sd(i) and corresponding time stamp cnt(i), which are obtained
according to the exemplary embodiments and/or exemplary methods of the
present invention, are not necessarily processed in the same
chronological sequence as they are received from transmitting network
node 200 in the area of communication interface 108. Rather, on the basis
of the present invention's assignment of the time stamps to the sensor
data values, a subsequent evaluation in block 112 may take place
completely detached from the arrival times of individual sensor data
values sd(i) in receiving network node 100a.

[0060] In a subsequent, optional step 310, signal processing may already
be performed in transmitting network node 200. For example, signal
processing 310 may include averaging over several sampling values or data
compression.

[0062] FIG. 5 shows a simplified flow chart of a specific embodiment of an
operational method for receiving network nodes 100, 100a of the exemplary
embodiments and/or exemplary methods of the present invention.

[0063] In a first step 400, digitally transmitted sensor data sd are
received from at least one transmitting network node 200 with the aid of
communication interface 108.

[0064] In a subsequent step 410, receiving network node 100 assigns
received sensor data values sd(i) one time stamp cnt(i) each, using time
stamp device 106; the time stamp representing a time of reception of
sensor data values sd(i) at network node 100 with respect to a primary
time reference 102 assigned to network node 100.

[0066] Finally, in step 430, a further evaluation of the received sensor
data or of the sensor data values sd(i) provided with time stamp cnt(i)
is performed.

[0067] According to the exemplary embodiments and/or exemplary methods of
the present invention, one may advantageously dispense with a network
node 200 transmitting sensor data sd having to perform time stamping
itself, as well as having to transmit sensor data sd, together with the
time stamps, to a receiving network node 100, 100a. In an advantageous
manner, the network nodes 100, 100a of the exemplary embodiments and/or
exemplary methods of the present invention that receive the sensor data
may themselves undertake time stamping, which defines the entry time of
the received sensor data with regard to primary time reference 102 of
receiving network node 100, 100a, so that subsequent processing of the
received sensor data may be carried out independently of any delay times
in receiving network node 100, 100a.